fsck doc: a minor typofix

Reword the misspelled "squelch" noticed by Hermann Gaustere to say
"omit", which would sit better anyway.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

Documentation/git-fsck.txt

@@ -33,7 +33,7 @@ index file, all SHA1 references in .git/refs/*, and all reflogs (unless
 --dangling::
 --no-dangling::
 	Print objects that exist but that are never 'directly' used (default).
-	`--no-dangling` can be used to squech this information from the output.
+	`--no-dangling` can be used to omit this information from the output.
 
 --root::
 	Report root nodes.